The present invention relates to a method for tartaric stabilisation, in particular for wine, and an apparatus for its implementation.
It is known that in wines, in must, in grape juices in general and in other drinks, potassium, tartaric acid and calcium are present in high concentrations. During the fermentation phase, potassium bitartrate, also known as tartar, is formed. Calcium tartrate can also be formed during the fermentation.
The wine, being therefore a supersaturated solution of potassium bitartrate, is subject to the precipitation of this salt. Similarly, the presence of calcium may constitute a further risk for the precipitation of the tartaric acid salt.
The complete precipitation of the aforesaid salts in crystalline form is a phenomenon which generally requires a long time and is influenced by various factors. Amongst such factors, for instance, are the quantity of ethanol present in the wine, the temperature at which the wine is preserved and the acidity of the wine itself.
It should be observed, in particular, that the aforementioned salts are less soluble in ethanol than in water. Therefore, simultaneously with the formation of ethanol due to the fermentation of the wine, and also thereafter, their slow and progressive precipitation takes place.
The presence of crystals or bottom bodies due to this phenomenon constitutes a serious drawback, in that it is generally not to the liking of the consumer who is thus discouraged from consuming the wine itself. The precipitation of the potassium bitartrate and calcium tartrate salts, in effect, may generally continue even after the bottling of the wine, severely damaging the image of the product.
It is therefore necessary to subject the wine to tartaric stabilisation processes in order to prevent the precipitation of the aforementioned annoying salts.
A first known technique for the tartaric stabilisation of wines exploits the lowering of the temperature, which facilitates the precipitation of potassium bitartrate but not of calcium tartrate. This property is still the most widely used both with traditional and continuous systems.
This known technique presents some drawbacks, in that its efficiency is not very high. In some particular cases it is ineffective and it causes the elimination of some substances that actually have beneficial effects on wine quality.
A second known technique provides for treating the wine with the use of electrodialysis with membrane filters, as shown for instance in the patents FR2709308, FR2192170 and IT971999.
Lastly, methods for the tartaric stabilisation of wine are known with the use of ionic exchange resins.
This last solution presents some drawbacks.
The resin treatment applied to all the wine leads also to the removal of aromatic and colouring substances, negatively influencing the quality of the wine itself.
By contrast, electrodialysis, also due to the limitations of currently available membranes, is very costly, requiring extremely sophisticated machinery.